I use a camera lens brush you can pick up at any Wolf Camera or similar type store. The soft lens brush will not scratch the plastic and the fine bristles get along the edges pretty well.... You can even get a small squeeze type blower brush to really clean the crevices if you're in to super detailing...

Wayne

2008 Toyota Camry Hybrid, Magnetic Grey, XM Radio, Body Side Moldings, Splash Guards, Formula 1 Pinnacle 35 Ceramic Window Tint, PadsPlus Neoprene Rubber Insert Set, Putco Chrome Door Handles, Michelin Primacy P215/60R16 95H Tires, SE Rear Spoiler